CELLULOSE-ACETATE PROPIONATE AND POLY(TETRAMETHYLENE GLUTARATE) BLENDS

Blends of a polyester, poly(tetramethylene glutarate) (PTG), and a cellulose ester, cellulose acetate propionate (CAP), in the range of 50-90 wt % CAP were prepared by thermal compounding. Carbon-13 NMR and gel permeation chromatography showed that no transesterification and little loss in molecular weight occurred during thermal mixing. Differential scanning calorimetry of PTG and of CAP cooled rapidly from the melt revealed that PTG is a low melting (39-degrees-C), low T(g) (-55-degrees-C), semicrystalline polymer while the CAP is an amorphous, high T(g) (136-degrees-C) polymer. These CAP/PTG blends are optically clear and, when quenched from the melt, amorphous. Some blend compositions did exhibit small crystallization exotherms and melting endotherms in I)SC experiments. The temperature of these melting endotherms decreased linearly from ca. 168 to 148-degrees-C with decreasing CAP content over the range 85-60% CAP, while the DELTAH(f) reached a maximum at 75% CAP in the blend; the glass transition temperature of these same blends agreed well with predicted values. These results indicate that CAP can crystallize from the solid-state solution under appropriate experimental conditions depending upon the content of amorphous polymer and upon the T(g)/T(c) gap.